Dementia in elderly adults: prevalence and institutionalization.

A formula for age-specific dementia prevalence is derived using data from a New Zealand study. Six other studies of dementia prevalence selected according to certain criteria are analyzed and their results shown to be not significantly different from those expected on the basis of the formula. Moreover, the small standard error estimate for the studies in aggregate indicates that the observed results are in close agreement with those expected. Dementia prevalence is estimated in both current and projected Australian aged populations using the age-specific prevalence formula. Comparison of the number of confused persons in institutions with the estimated number in the total population suggests that almost half of the moderate or severe dementia cases may be institutionalized, a much higher proportion than reported in other studies. Variations in overall levels of institutionalization are suggested as the main reason for such differences.